Conventionally, an incandescence lamp, which has a filament in a tube, is frequently used as a heat source. For example, as described in Japanese Patent Application Publication No. 2001-126846, a halogen heater is used in a fixing apparatus for an image forming apparatus, such as a copying machine, a printer, or a facsimile, wherein the thickness of the lamp is made smaller than that of the conventional glass tube (tube), thereby improving the transmittance of light thereof.
Moreover, an incandescence lamp unit, in which two or more incandescence lamps are arranged so as to correspond to the sizes of recording paper sheets, is also known. Japanese Patent Application Publication No. 2009-117147 discloses an example thereof, and FIG. 5 shows the schematic structure thereof, wherein a lamp unit 30, which consists of two or more rod-shaped heater lamps 31 and 32, is arranged as a heat source inside a heating roller which forms a heating fixing apparatus (not shown in the figure). In this apparatus, a filament 33, which is a light emission part, is arranged in the central part of one incandescence lamp 31, and internal leads 34 and 35, which are non-light emitting portions, are arranged at both sides thereof. Filaments 36 and 37 are arranged in the other incandescence lamp 32 so as to be shifted from the filament 33 of the one incandescence lamp 31, and are connected to each other by an internal lead 38.
The lamp unit 30 turns on each lamp according to the size of recording paper. For example, in case where the size of recording paper is A4, only the lamp 31 is turned on, and in case where the size of recording paper is A3, both of the lamps 31 and 32 are turned on.